Tire having an element or covering attached to a surface thereof

ABSTRACT

A tire is provided, on a surface thereof, an applicaiton having a top layer exposed to the air and a bottom layer in contact with the tire. The top layer can be a rigid element and/or a marking covering, or a device for measuring or monitoring the tire. The bottom layer is a foam having a void ratio of at least 40%, a thickness of at least 0.5 mm, and a density ranging from 0.02 g/cm 3  to 0.5 g/cm 3 .

This application is a continuation of International ApplicationPCT/EP04/000342 filed on Jan. 19, 2005 and which published as WO2004/065140 on Aug. 5, 2004.

BACKGROUND

The invention concerns the application of coverings and/or elements tothe surface of rubber articles, in particular tires. More particularly,it concerns the application of these elements and/or coverings after thevulcanization of such articles. The invention concerns in particular themarking, colored or not, of part of the surface of the tire by applyinga rigid or non-rigid element and/or a covering.

The tires can carry, for decorative or identification purposes, amarking, colored or not, directly applied to part of the generallyexternal surface of the tire. “Marking” means, in the text, any elementor covering affixed to the said surface of the tire, generally after itsvulcanization. This marking can consist of a so-called rigid element, asoft element, a layer of lacquer, a coat of paint, etc.

“Rigid element” means elements incapable of following the successivedeformations of a tire when it is running. These so-called rigidelements can according to circumstances be completely non-deformable orflexible but non-elastic to the scale of the deformations of the tire.In other words, they can, where necessary, bend but be incapable offollowing the local variations in the area of the surface of the tirefollowing changes in radius of curvature of the said tire. Theseelements can consist of metal, plastic, elastomer, ceramic, etc.

The marking of a tire, produced in an appropriate material, can be inone or more colors, including white. However, producing markings,colored or not, on tires poses great difficulties.

Such markings are intended to cover at least part of the surface oftires. Since it is a case of a surface covering, these markings areparticularly intended to cover surfaces of tire covers said to be“non-wearing”, that is to say which are not in contact with the roadunder normal conditions of use of the said tires. Thus such coloredmarkings, having decorative and identification purposes in particular,can constitute at least partially the external surface of a tire coversidewall or groove bottoms of the tread.

The complexity of directly covering the surface of tires with suchmarkings is well known to persons skilled in the art. There exist infact two major difficulties in this implementation, firstly the natureof the compositions in the tire which acts on the markings, as will beseen more explicitly below, and secondly the stresses to which the tireis subjected when it is running which cause significant deformations ofthe tire and therefore of its surface, to which the markings must beable to adapt.

The vulcanized compositions of diene rubbers, both natural andsynthetic, because of the presence of double bonds on their molecularchains, are liable to deteriorate more or less rapidly after prolongedexposure to the atmosphere, because of known mechanisms of oxidation andozonolysis. These degradation mechanisms are also accelerated under thecombined action of heat by thermo-oxidation, or that of light byphoto-oxidation (see for example: “Photo-oxydation and stabilisation ofpolymers”, Trends in Polym. Sci., Vol. 4, No 3, 1996, 92-98;“Degradation mechanisms of rubbers”, Int. Polym. Sci. and Technol., Vol22, No 12, 1995, 47-57).

It has been possible to inhibit all these phenomena of degradation ofthe tire, linked to its aging, little by little by virtue of thedevelopment and introduction into diene rubber compositions intended forthe manufacture of tires of various antidegrading agents such asantioxidants or antiozonants. Compounds have even been found which areable to fulfil these two functions simultaneously; the most effective,both as antioxidants or antiozonants, are in a known manner derivativesof quinoline, such as for example 2,2,4-trimethyl-1,2-dihydroquinoline(“TMQ”) or derivatives of p-phenylenediamine (“PPD”) even more activethan the first, such as for exampleN-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine (“6-PPD”) orN-isopropyl-N′-phenyl-p-phenylenediamine (“I-PPD”). These antidegradantsof the TMQ and PPD type, sometimes even combined, are today verywidespread and used in an almost routine manner in conventional dienerubber compositions filled at least partly with carbon black, givingthem their characteristic black color.

However, the agents cited above, in particular TMQ or PPD derivatives,are not stable under light and, under the effect of UV radiation,generated colored chemical substances which cause an impairment of thecolor of the rubber compositions containing them, staining them darkbrown.

In addition, antidegradants are mobile on the molecular scale within therubber composition containing them. This mobility extends to thecompositions adjacent to that initially containing the antidegradants.Thus these antidegradants are liable to migrate into a colored markingcomposition fixed to the rubber composition containing them, and tostain it.

Moreover, in order to limit the degradation due to ozone, elastomercompositions also normally incorporate waxes which, statically, affordadditional protection with respect to antiozonants by the formation of aprotective surface coating. However, the waxes, which are alsocharacterised by their ability to migrate as far as the surface of therubber articles, modify the external appearance of the surfaces of theelastomer compositions by staining them or making them dull and grey.This phenomenon is referred to as the “blooming” of the waxes.

This is why it is extremely complex to produce a marking of durableappearance, colored or not, intended to cover part of the externalsurface of tire covers resisting staining and alteration due to theantioxidants, antiozonants and waxes present in the elastomercompositions used in tires.

The majority of solutions propose the development of color markingswhose composition combines both the various constituents for obtainingcolor and non-migration of the waxes or staining products. However, itis also necessary, as stated, for the marking to be capable of enduringthe mechanical stresses to which the tire is subjected.

However, the solutions to these two problems which are accessible at thepresent time are often opposing and are therefore not satisfactory forimproving the compromise between durable appearance and resistance tomechanical stresses. This is because:

-   -   when the covering is sufficiently flexible to accommodate        repeated deformations throughout the life of the tire, the        molecular mobilities are too great therein for completely        preventing the migrations of these staining products;    -   when the coating is rigid, thus restricting the molecular        mobility, it is no longer capable of following the deformations        of a tire without causing excessively great concentrations of        stresses which, according to circumstances, will result in a        detachment or breakage of the covering.

It therefore proves necessary, in order to obtain durable marking, to beable at least to reduce or even eliminate the impairment of the colorand/or the brightness of the marking affixed to the external surface ofa tire, whilst conferring on it an ability to accommodate deformationsof the tire.

SUMMARY OF THE INVENTION

The applicant has discovered in a surprising fashion that one way ofresolving both the problem of a chemical nature and the problem of amechanical nature related to the marking of a tire comprises interposinga layer of foam between the part of the surface of the tire to be markedand the marking element and/or covering. The layer of foam and themarking element and/or covering form a stack of two layers, hereinafterreferred to in the text as an application.

In addition, it is more and more being sought to store information inelectronic chips integrated in or fixed to the tire, and to makemeasurements, in particular pressure and/or temperature monitoring,which require the use of sensors or other signal connection,communication, transmission or reception systems. These devices, whichrequire rigid supports, pose real problems of fixing to the tire sincethey cannot follow the deformations of the tire. This is why thesolution afforded by the invention also makes it possible to surmountthe problems of fixing these devices to the tire.

Consequently a first object of the invention consists of a tirecomprising, on at least part of its surface, at least one application,characterized in that the said application is composed of a first layer(e.g, a marking or covering or other element in contact with the airconstituting the top layer of the application and a second layer incontact with the tire constituting the bottom layer of the application,said bottom layer of the application comprising a visible and verydeformable low-density foam.

In the text, for a stack of layers, the terminology “bottom” will beadopted to designate the layer/surface in contact with the tire andclosest to the carcass ply and “top” to designate the layer/surfacefarthest away from the carcass ply, in particular in contact with theair.

The solution afforded by the inventors of interposing foam between thesurface of the tire and the marking element and/or covering allowschemical decoupling in order to prevent chemical exchanges by migrationand therefore the staining of the said covering and/or element, withoutits being necessary for the latter itself to possess characteristics ofimpermeability, and to simultaneously achieve a mechanical decoupling inorder to preserve the fixing of the said covering and/or element and itsform.

DESCRIPTION OF THE DRAWING

Other characteristics and advantages of the invention will emerge from areview of a preferred example embodiment of a tire according to theinvention, with reference to the accompanying drawing in which FIGS. 1-3each depict a radial half-section of a tire carrying a marking accordingto the invention, and to a review of the method of fixing to the tire amarking covering and/or element according to the invention.

FIG. 1 depicts a radial half-sectioin of a tire according to a firstembodiment of the invention.

FIG. 2 depicts a radial half-section of a tire according to a secondembodiment of the invention.

FIG. 3 depicts a radial half-section of a tire according to a thirdembodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

The marking of a tire constitutes one aspect of the invention. Thisaspect is described here purely by way of example and is not intended toconstitute a limitation to the invention. A person skilled in the artwill understand that the invention also comprises the fixing to thesurface of the tire of an element and/or covering intended for purposesother than marking, such as the fixing of monitoring, measuring, etc.devices.

Thus, by way of example, the accompanying figure depicts schematically aradial half-section of a tire 1 with carcass reinforcement. This tire 1comprises in the figure a crown 2, a sidewall 3, a bead 4, a carcassreinforcement 6 extending from one bead to the other. The crown 2 issurmounted by a tread 7. The carcass reinforcement 6 is wound around thetwo bead wires 5 (only one being shown on the half-section in thefigure) in each bead 4.

The invention thus concerns a tire 1 comprising on at least part of itssurface at least one application 8 according to the invention. The partof the tire on which the application according to the invention is fixedhas a rubber composition based on at least one essentially saturateddiene elastomer, at least one essentially unsaturated diene elastomer ora mixture of these two types of elastomer. The rubber composition cancontain conventional additives and in particular agents for protectionagainst ozone, oxidation, etc.

“Diene” elastomer means in a known manner an elastomer issuing at leastpartly (i.e. a homopolymer or a copolymer) from diene monomers (monomerscarrying two double carbon-carbon bonds, conjugate or not). These dieneelastomers can be classified in two categories: “essentiallyunsaturated” or “essentially saturated”.

In general terms, “essentially unsaturated” diene elastomer means adiene elastomer issuing at least partly from conjugated diene monomers,having a level of units of diene origin (conjugated dienes) which isgreater than 15% (% molar).

Thus, for example, diene elastomers such as butyl rubbers or copolymersof dienes and alpha-olefins of the EPDM (ethylene-propylene-dieneterpolymer) type do not fall within the above definition and can inparticular be termed “essentially saturated” diene elastomers (low orvery low level of units of diene origin, always less than 15%).

According to one embodiment of the invention shown in FIG. 1, the partof the tire to which the application according to the invention is fixedis the sidewall of the tire. The accompanying figure illustrates thisembodiment and more particularly a fixing of the application 8 to theradially bottom or inner part of the sidewall 3. The composition of thispart of the tire can then contain at least one essentially saturateddiene elastomer, in particular at least one EPDM copolymer, whether thiscopolymer be for example used or not in a mixture with one or more ofthe essentially unsaturated diene elastomers.

According to another embodiment of the invention shown in FIG. 2, thepart of the tire to which the application according to the invention isfixed is an internal tire rubber compound or any other layer or objectimpermeable to air. The composition of this part of the tire can thencontain at least one essentially saturated diene elastomer of theisobutene and isoprene copolymer (butyl rubber) type, as well as thehalogenated versions of these copolymers.

According to yet another embodiment of the invention shown in FIG. 3,the part of the tire to which the application according to the inventionis fixed is the tread, in the particular the groove bottoms of thetread. The composition of this part of the tire can then contain atleast one essentially unsaturated diene elastomer.

Referring to FIG. 1, the application 8 according to the invention thuscomprises a first layer 9 in contact with the air constituting the toplayer of the application and a second layer 10 in contact with (exposedto) the tire constituting the bottom layer of the application. Thisbottom layer 10 of the application consists of a visible very deformablelow-density foam. It affords chemical and mechanical decoupling betweenthe surface of the tire and the top layer of the application,constituting the marking element and/or covering.

The layer of foam composing the bottom layer 10 of the application 8according to the invention consists of a low-density foam having a highvoid ratio. This opposes chemical migrations and thus prevents or verygreatly limits the migrations of the staining agents contained in theelastomer mixture constituting the part of the tire to which the tireapplication is fixed. This is because the high void ratio and the lowdensity gives rise to a decrease in the cross-section of passage andextension of the path all along the walls of the cells of the foamthroughout the thickness of the foam. Naturally, this effect is alsoclosely linked to the thickness of the layer of foam.

The limitation of the migration of the staining agents can be reinforcedby a careful choice of the material making up the foam, which can havecharacteristics of impermeability of the foam material vis-a-vis themigrants.

Moreover, the advantage of a foam is clearly to have a sufficientflexibility of structure to follow the deformations of the tire.

It is thus possible to choose various kinds of material for forming thisfoam, its thickness, its void ratio and its density being, as juststated, directly linked to this choice.

In general terms, the layer of foam can have a thickness of at least 0.5mm. Below this value, the chemical and mechanical decoupling will not besufficient to allow a durable marking through its appearance andstrength.

In general terms, when the application is fixed to part of the externalsurface of the tire, it should not project by more than 3 mm from thesurface of the tire. The external surface of the tire is the visiblesurface of the tire which is not in contact with the inflation air. Thisis because the application projecting from the tire 1 beyond this value3 mm would greatly increase the risk of tearing away of the saidapplication.

In general terms, when the application is fixed to part of the surfaceoriented towards the cavity of the tire, in particular the internalrubber compound, it may have a thickness much greater than 3 mm.However, an excessive weight fixed to the inside of the tire wouldresult in unbalancing it too greatly. Thus the thickness of theapplication will also depend on the density of the foam and the natureof the top layer. By way of example, it is nevertheless possible toenvisage applications with a thickness ranging up to approximately 3 cmfor fixing to part of the surface oriented towards the cavity of thetire.

According to one advantageous embodiment of the invention illustrated bythe figure, with a view to anchoring of the application 8 and thereforebetter fixing of the application 8, the latter will be fixed in a cavity11 of appropriate size, provided for this purpose in the tire 1. Thiscavity, which should have a depth of no more than the thickness of theapplication 8, is advantageously formed during the molding of the tire1.

In general terms, the foam can have a density of at least 0.02 g/cm3,measured in a conventional manner. Below this limit the foam would nothave sufficient mechanical strength. That is to say, below this value,the foam would deform too easily and, under the effect of centrifugalforce, it might tear. The foam can have a density ranging up to 0.50g/cm3. By way of example, the density of the foam can range from 0.05g/cm3 to 0.30 g/cm3.

In general terms, the rigidity of the foam will advantageously be lessthan the rigidity of the material with the lowest rigidity to bedecoupled. Preferentially, this difference should be at least 50%. Evenmore preferentially, the rigidity of the foam should be at least 3 timesless than the rigidity of the material with the lowest rigidity to bedecoupled. The rigidity is expressed by the modulus of extension at 10%elongation, measured in a conventional manner.

Another characteristic of the foam which can be used in the context ofthe invention is its void ratio. In general terms according to theinvention the void ratio will advantageously be at least 40% so that thefoam is sufficiently compressible. This void ratio can be calculated bycomparing the density of the foam with that of the compact materialconstituting its matrix, measured by any conventional means.

The foam constituting the bottom layer of the application according tothe invention will have at least one of the characteristics specifiedabove relating to density, rigidity and void ratio. It willadvantageously have at least two of those characteristics and, moreadvantageously still, it will have all of the following characteristics:

-   -   a void ratio of at least 40%,    -   a thickness of at least 0.5 mm, and    -   a density ranging from 0.02 g/cm³ to 0.5 g/cm³.

Nevertheless, the characteristics of the foam stated above also dependon the nature of the materials for forming this foam. A person skilledin the art will know how to determine the characteristics required for agiven material.

It is thus possible to choose an elastomer foam for which a specificdensity of 0.05 to 0.40 g/cm³ represents a good working compromise. Itis possible for the density to be situated particularly between 0.1 and0.3 g/cm³, for example ranging from 0.1 to 0.25 g/cm³.

Among the materials which may constitute the matrix of these elastomerfoams, there can be cited thermosetting elastomers such as naturalrubber, polyisoprene, polybutadiene, butadiene-stirene, butyls,halogenated polycholoroprene butyls, polyepichloridrines, polyacrylics,polysulphides, chlorinated polyethylenes, chlorosulphonatedpolyethylenes, alkyl-chlorosulphonated polyethylenes, EPT (ethylenepropylene termonomer), EPDM (ethylene-propylene-diene terpolymer),nitrile (NBR) and hydrogenated nitrile (HNBR), silicones, fluorinatedelastomers, etc.; polyurethanes, polyureas, polyurethane-ureas;thermoplastic elastomers based on block polymers such as stirenepolymers (SBS, SEBS, MBS, etc.) polyetheramides (PEBA, etc.), polyetheresters and copolyesters, thermoplastic polyurethanes (TPU), vinyls(vinyl ethylene acetate copolymers, etc.) etc.; thermoplastic elastomersbased on elastomer alloys or mixtures such as TPOs (thermoplasticpolyolefins: EPDM+EPDM polypropylene+HD polyethylene, vinylpolychloride+vinyl polyacetate, TPU+polycarbonate, natural rubber orpolyisoprene+polypropylene, NBR+polyvinyl chloride; cross-linkedthermoplastic elastomers.

It should be noted that the foams composed of no more than 80% butylelastomers are particularly advantageous because of their very goodimpermeability to staining agents. Note that this maximum level of butylis related to the obtaining of good adhesion on surfaces consisting ofessentially unsaturated diene elastomers.

It is also possible to choose non-elastomeric foams for which it will beadvantageous to choose a lower specific density of around 0.02 to 0.10g/cm³.

It is thus possible to cite by way of non-elastomeric foams, normalplastics chosen from amongst polyolefins, polyvinyls, stirenes,acrylics, polyacetals, polyamides, polyesters, polycarbonates,polyoxyphenylenes, phenylene polysulphides, polyimides, polysulphones,polycycloolefins, polyketones, as well as mixtures and alloys thereof.

It is possible to choose foams with closed or open cells. In the case offoam with open cells a skin will have to surround the layer of foam inorder to prevent possibilities of penetration of water when it is a caseof an application on the external surface of the tire. This skin can beformed during the manufacture of the foam (integral foam) or appliedsubsequently (by bonding, lacquering, etc.).

In the case of a foam with closed cells, the skin is less essential butmay be useful in order to have a surface which is smoother and thereforemore aesthetic and easier to decorate.

For applications internal to the tire, in particular on the internalrubber compound, the decoupling foam will preferably have open cells inorder not to be subjected to compression by the inflation air.

The element and/or covering constituting the top layer 9 of theapplication 8 to be affixed to the tire 1 can be in the form of:

-   -   a flexible layer which it is wished to decouple chemically in        order to prevent migrations of agents constituting the rubber        composition making up the part of the tire on which the marking        element and/or covering is affixed, and/or to mechanically        decouple in order to prevent any delamination, cracking, etc.        This may be a layer of elastomeric mixture, colored or not, a        layer of elastomeric paint, a layer of elastomeric lacquer,        colored or not, etc.;    -   an essentially decorative rigid element, to be decoupled        mechanically and possibly chemically. It may for example consist        of a layer of rigid paint, a layer of rigid lacquer, colored or        not, a plate, a sheet, a fabric, a molded or machined object,        etc., made from any elastomeric, plastic, ceramic or metallic        material, bare or decorated, which allows a choice of any        pattern or color. It appears advantageous to effect the marking        with so-called rigid elements rather than soft, on the one hand        because it is possible to obtain objects of durable appearance        by pressing, injection, etc. The rigidity of these objects        substantially decreases the molecular mobility;    -   a rigid functional element such as for example, comprising in        particular an electronic device, such as a sensor, an electronic        chip, an electrical supply cluster, a reception or transmission        antenna, or a layer of connection threads enabling the tire to        receive or transmit information, with or without contact patch.        Contact patch means the slug or base, generally elastomeric, on        which these elements are fixed, removably or not, which allows        the fixing of the assembly on the tire. Such elements are known        to persons skilled in the art. By way of example, the elements        described in EP-1,254,787, U.S. Publication 2002/0124934, and        EP-1,006,167 can be cited.

The method of marking at least part of the surface of a tire 1 accordingto the invention comprises the following steps:

the affixing of the marking 9 on the top part of a layer of foam 10 ofappropriate size thus forming a stack which will be referred to as theapplication 8, fixing the said application 8 by bonding the bottom partof the said layer of foam 10 to the part of the surface of the tire 1 tobe marked.

Affixing of the marking, element and/or covering means the fixing ofthis marking to the foam by any appropriate means, such as in particulartransfer, adhesive bonding, etc.

The method of fixing a rigid element, other than a marking, to at leastpart of the surface of the tire is similar. It comprises the steps offixing, generally by adhesive bonding, the rigid element to the top partof a layer of foam of appropriate size forming an application, andfixing the said application by adhesive bonding of the bottom part ofthe layer of foam to the required part of the surface of the tire.

Various adhesive bonding methods can be used for bonding the layer offoam 10 to the surface of the tire 1, as well as for the bonding of thetop layer 9 of the application 8 (marking or other element to be fixed)on the layer of foam 10.

For bonding the foam to the surface of the tire, the adhesive should beelastomeric in order to be able to follow the deformations of the tire.

For bonding the top layer 9 of the application 8 on the layer of foam10, the rigidity of the adhesive has less importance since the topsurface of the layer of foam 10 in contact with the top layer 9 of theapplication 8 is not deformed or only a little.

To simply the affixing, it is advantageously possible to use the sameadhesive for constituting an adhesive surface which can be reactivatedthermally.

For example, it is possible to use a self cross-linking polyurethanelatex such as that sold by the company Avecia under the trade name“Neo-Rez R-550”, depositing the latter on each of the surfaces to beassembled (the surface of the tire, the two surfaces of the layer offoam and the bottom surface of the top layer of the application). Notethat, for the surfaces not directly having polar functions capable ofbonding chemically with the polyurethane, it is necessary to provide anintermediate treatment, for example with a solution based ontrichloro-isocyanuric acid (TIC) at 2 or 3% in an organic solvent,generally ethyl acetate.

The surface of the vulcanized tire is thus made to undergo a treatmentin order to make the elastomers on this surface polar and tofunctionalize them. At least one layer consisting of an aqueousdispersion of polyurethane is applied to this treated surface and thislayer is left to dry. The application of the aqueous dispersion ofpolyurethane can be carried out at room temperature. Thus this methodcan easily be implemented on the vulcanized tire without moreoverrequiring any heating operation, although it is possible, through amoderate rise in the temperature on the surface of the tire, toaccelerate the drying operations.

It is also possible to use commercial adhesive foams spread with acrylicadhesive such as the foam sold by the company “3M” under the references4416, which is a vinyl foam, and 4965 P, which is a neoprene foam.

The following examples illustrate the invention without however limitingit.

EXAMPLE 1

The samples of application used for these tests were bonded on a tiresidewall of the PAX 205-650 R 440 type, in the radially bottom part ofthe sidewall.

The elastomeric composition of the radial bottom part of the sidewall isbased on a blend of elastomers containing natural rubber andpolybutadiene, protected against ozone and oxidation by a mixture of6-PPD, IPPD and TMQ.

The samples of application were produced in the form of small plates inportions of a ring with a length of 70 mm to a width of 5 mm, with, asthe bottom layer in contact with the tire, a butyl foam sold under thename Bib Mousse by Michelin with 80% elastomer, with a density of 0.13g/cm3, a void ratio of 88% and a thickness of 1.9 mm, to which there isfixed, with an adhesive B, a decorative rigid element A for whichseveral materials have been tested.

The materials A1-A3 tested for the decorative rigid element are asfollows. The dimensions of these elements, apart from their thickness,are the same as those of the foam in the bottom layer:

-   -   A1: polycarbonate sold under the name Meraklon by Bayer, with a        thickness of 0.3 mm    -   A2: a polyester, PET (polyethylene terephthalate) with a        thickness of 0.5 mm sold by Xtreme    -   A3: a PVC, with a thickness of 0.3 mm.

Two methods of adhesive bonding were used:

Adhesive bonding B1: polyurethane latex sold under the trade nameNeo-Rez R-550 by Avecia for bonding the decorative element A to the foamand for bonding the foam to the tire. In the latter case, the surface ofthe tire is treated with a solution of TIC.

Adhesive bonding B2: for bonding the decorative element A to the foamand for bonding the foam to the tire. In the latter case, the surface ofthe tire is first of all treated with a solution of TIC and then coveredwith an adhesive based on polyurethane in accordance with Example 1 ofthe document EP-1 178 097, integrated in the present description byreference.

These samples were compared with a reference not comprising the bottomlayer of foam. By way of reference, the rigid element A2 directly bondedto the tire sidewall was tested.

The tires carrying these various samples were mounted on passenger carsof the Peugeot 806 type. These vehicles were subjected to running on theroad at a maximum speed of 110 km/h over a distance of between 1500 and2000 km. At the end of this running, a first observation of the tireswas carried out. Then a second running of approximately one thousandadditional kilometers was carried out under the same conditions, at theend of which the wheels carrying the tires were removed in order to makethe observation of the samples more thorough.

The results obtained are entered in the following table.

Sample Reference A1 with A2 with A3 with without foam foam foam foamRigid PET polyester Polycar- PET PVC element bonate polyester AdhesiveB1 B1 B1 B2 1st Unstuck at NTR* at NTR* at NTR* at obser- 68 km 2000 km2000 km 1500 km vation 2nd NTR* at NTR* at NTR* at obser- 3600 km 3600km 3000 km vation NTR: no unsticking, cracking or pulling away

It is found that, in accordance with the invention, marking by means ofan application allows durable marking of the tire. The layer of foamenables the rigid marking element to be decoupled from the deformationsof the tire, thus preventing any rupture or unsticking of the said rigidelement.

EXAMPLE 2

During further tests, a sample of application was bonded to the sidewallof a tire of the PAX 205-650 R 440 type.

The elastomeric composition of the sidewall is based on a blend ofelastomers containing natural rubber and polybutadiene, protectedagainst ozone and oxidation by a mixture of 6 PPD, IPPD and TMQ.

The preservation of the appearance of this sample was tested bycomparing it with a sample not comprising the bottom layer of foam anddirectly bonded to the tire sidewall.

The sample of application was produced in the form of a small plate in aportion of a ring with a length of 70 mm and a width of 5 mm, with, asthe bottom layer in contact with the tire, an adhesive polyurethanefoam, associated with an acrylic adhesive, sold by “3M” under thereference Ref. 4085. This foam has a density of 0.3 g/cm3, a void ratioof 70% and a thickness of 1.1 mm.

To this foam there is fixed a decorative stainable elastomeric elementwith a thickness of around 0.5 mm. This decorative element, reference“Mixture” in the table, is produced from the following elastomericcomposition:

100 pce 97% synthetic polyisoprene with a cis-1,4 structure sold byNizhnekamsk under the reference IR6596  40 pce Zéosil1165 M silica fromRhodia  10 pce Titanium oxide TiO2 of the octahedrite variety  2 pcePeroxide: 1,4-bis(tert-butyl peroxy-isopropyl)benzene  2 pce carbonblack N772

The unit “pce” means parts by weight per 100 parts by weight ofelastomer.

This element is fixed to the foam after having been previously treatedwith a solution of TIC. The application is fixed to the tire by adhesivebonding of the bottom face of the layer of foam to the sidewall. Thesurface of the tire is previously treated with a solution of TIC.

The reference consists of a strip of the same size of an elastomericmixture constituting the above stainable decorative element. Thereference is bonded to a tire sidewall under the same bonding conditionsby means of the adhesive sold under the reference Neo-Rez R.550 byAvecia.

The tires carrying sample and reference were mounted on passenger carsof the Peugeot 806 type. These vehicles were subjected for 3 months torunning on the road at a maximum speed of 110 km/h over a distance ofbetween 3000 or 4000 km. At the end of this running, an observation ofthe tires was carried out.

The results obtained are entered in the following table.

Sample Reference: marking without foam Marking with foam Bottom layer —Polyurethane foam* Top layer Mixture Mixture Observation at the endStaining of marking No staining of 3 months *Polyurethane foam: Ref.4085 from “3M”

With marking by means of the application according to the invention, nomajor modification of the appearance of the rigid marking element basedon elastomers is observed. It does not tarnish, nor become discolored.Its coloring remains the same range of color as before the runningtests.

1. A tire including an interior surface facing a center axis of thetire, and an external surface including a tread and a sidewall, the tirecomprising at least one application disposed entirely on a surfaceportion of the external surface, the application including a first layerconstituting a top layer in contact with air, and a second layerconstituting a bottom layer in contact with the tire surface portion,the bottom layer comprising foam having a void ratio of at least 40%,wherein the foam comprises at least one plastics material with a densityranging from 0.02 to 0.1 g/cm³.
 2. The tire according to claim 1 whereinthe foam has a thickness of at least 0.5 mm.
 3. The tire according toclaim 2 wherein the foam has a thickness is in the range of from 0.5 mmto 30 mm.
 4. The tire according to claim 1 wherein the surface portionis that of the tread.
 5. The tire according to claim 4 wherein thesurface portion comprises a groove base of the tread.
 6. The tireaccording to claim 1 wherein the surface portion is that of the sidewall.
 7. The tire according to claim 1 wherein the top layer comprises amaterial selected from plastic, elastomer, ceramic and metal.
 8. Thetire according to claim 1 wherein the top layer comprises a materialselected from paint and lacquer.
 9. The tire according to claim 1wherein the top layer comprises one of: a sensor, an electronic chip, anelectrical supply cluster, a connector, a reception antenna and atransmission antenna.
 10. A tire comprising at least one applicationdisposed entirely within a cavity disposed in a surface portion of thetire located radially inwardly of a radially outermost face of a treadof the tire, the application including a first layer constituting a toplayer in contact with air, and a second layer constituting a bottomlayer in contact with the tire surface, the bottom layer comprising foamhaving a density in the range of from 0.02 g/cm³ to 0.5 g/cm³, whereinthe cavity is defined by a groove of the tread.
 11. The tire accordingto claim 10 wherein the foam has a void ratio of at least 40%.
 12. Thetire according to claim 11 wherein the foam has a thickness of at least0.5 mm.
 13. A tire comprising, on at least a part of a surface thereof,at least one application including a first layer constituting a toplayer in contact with air, and a second layer constituting a bottomlayer in contact with the tire surface, the bottom layer comprisingfoam, the application attached to the tire surface solely at the foam byan adhesive, the foam having at least one of the following properties:A) a void ratio of at least 40%, B) a thickness of at least 0.5 mm, andC) a density in the range of from 0.02 g/cm³ to 0.5 g/cm³ wherein thetop layer comprises one of: a sensor, an electronic chip, an electricalsupply cluster, a connector, a reception antenna and a transmissionantenna.
 14. A tire comprising at least one application disposedentirely on a surface portion of the tire situated radially inwardly ofa radially outermost face of a tread of the tire, the applicationincluding a first layer constituting a top layer in contact with air,and a second layer constituting a bottom layer in contact with the tiresurface, the bottom layer comprising foam, the application attached tothe surface portion solely at the foam by an adhesive, the foam havingall of the following properties: A) a void ratio of at least 40%, B) athickness of at least 0.5 mm, and C) a density in the range of from 0.02g/cm³ to 0.5 g/cm³ wherein the application is mounted within a cavityformed in the surface portion of the tire.
 15. A tire comprising, on atleast a part of a surface thereof, at least one application including afirst layer constituting a top layer in contact with air, and a secondlayer constituting a bottom layer in contact with the tire surface, thebottom layer comprising foam having at least one of the followingproperties: A) a void ratio of at least 40%, B) a thickness of at least0.5 mm, and C) a density in the range of 0.02 g/cm³ to 0.5 g/cm³ whereinthe top layer comprises a material selected from paint and lacquer. 16.A tire comprising at least one application disposed entirely on asurface portion of the tire located radially inwardly of a radiallyoutermost face of a tread of the tire, the application including a firstlayer constituting a top layer in contact with air, and a second layerconstituting a bottom layer in contact with the tire surface, the bottomlayer comprising foam having a void ratio of at least 40%, wherein thetop layer comprises one of: a sensor, an electronic chip, an electricalsupply cluster, a connector, a reception antenna and a transmissionantenna.
 17. A tire comprising at least one application disposedentirely on a surface portion of the tire located radially inwardly of aradially outermost face of a tread of the tire, the applicationincluding a first layer constituting a top layer in contact with air,and a second layer constituting a bottom layer in contact with the tiresurface, the bottom layer comprising foam having a void ratio of atleast 40%, wherein the top layer comprises a material selected frompaint and lacquer.